A group of migrant workers from Florida stop in Sawboro, North Carolina, on their way to Cranberry, New Jersey, to pick potatoes in July 1940. The Green Book gave advice on safe places for black travellers to eat, get petrol and sleep. Photograph: Corbis via Getty Images

Over a barbecue grill last summer in a park in Springfield, Missouri, Jonathan Herbert and his friend Marlin Barber fell to ruminating about the challenges they faced as African Americans when driving across thecountry.

Barber, who teaches history at Missouri State University, was planning a road trip to Arkansas with his white wife and two young children, and was apprehensive about what they might encounter in the rural backwaters. Herbert had an idea why not float the dilemma to friends on Facebook and see what came back?

Sadly, its 2017, Herbert went ahead and posted, and we still have to consider the racial climate of some of the most beautiful places in this country before we decide to vacation there with our families.

The comment sparked intense Facebook reaction. A black friend divulged the fact that he had been called the N-word in Oklahoma and had run into the KKK in Texas. I remember not taking our kids through parts of Missouri or Arkansas out of fear, he said.

A white woman lamented that, in this day and age, her black friends still had to think twice about where they could go. This knocks the breath out of me. Your beautiful family has to consider factors mine doesnt. WTF, America?

The guide was the brainchild of Victor Green, a Harlem postal worker who spotted a market for travel tips directed at the growing car-owning black middle class. He compiled a list of hospitableoutlets to be sold through mail order. Tiny and slim, with a green cover in a riff on the writers name, the guide punched above its weight. Green defined its purpose demurely, saying it was intended to make travelling better for the Negro.

His readers would have easily decoded that phrase. In the 1930s, 40s and 50s, black drivers in the US had to be precise about their travel get it wrong and at best they could expect to be turned away in humiliating fashion, at worst they might end up lynched or shot.

What struck me when I first opened the Green Book was that it is all about the practicality of racism, says Michelle Johnson, who has written a play, The Green Book Wine Club Train Trip, that uses the travel guide as a device. Born in 1964, the year the Green Book went out of publication, Johnson is convinced that its premise that same inquiry Herbert posed on Facebook, Where is it safe to drive? has never ceased to be relevant.

Whenever I step out of the house Im on alert. When I drive through small-town Missouri, I put my armour on and am super-vigilant.

With those words ringing in my ears, I set out on a 900-mile drive, making a giant loop through Missouri, tracking down premises listed in the Green Book that are still standing and talking to black Missourians about their experiences today. Could Michelle Johnson be right? More than half a century after Jim Crow segregation was abolished, a new, social media-fuelled Green Book is once again needed?

The premises include a lodging house in Cape Girardeau, a couple of old rest homes in Springfield, and most evocatively, Sara-Lous cafe in St Louis, an old diner I found in a state of abject disrepair but still sporting its signage boasting Chicken Steaks Frogs.

Part of the chilling resonance of the guide, of course, is what it does not record the hundreds of thousands of hotels, motels, restaurants and petrol stations across the States that were actively hostile towards black people. So for the first stop on our three-day trip we decided to take a peek at a town that makes no appearance in any edition of the book, to find out what those Green Book users were trying to avoid. We headed for Sullivan, 70 miles south-west of St Louis.

Stefan Wehmeyer came to live in Sullivan eight years ago. As a mixed-race child of a white mother and estranged African American father, he had been warned before coming that the town had a bad reputation. Nothing prepared him for Sullivan.

On the first day Wehmeyer and his mother spent in their new home, they had a visit from their next-door neighbour. He was a giant of a man, around 6ft 5ins and 170kg (27 stone). He stood before them both but only addressed Wehmeyers mother, as though Wehmeyer himself were invisible.

If your son ever goes on my property Ill kill him, the man warned her. I dont like niggers on my property.

Wehmeyer was 13 years old. He didnt know it then, but Sullivan for decades had held an open secret: it was a sundown town. Well into the 1990s, black people unlucky enough to find themselves within its limits after dark could expect a rude awakening.

According to James Loewen, an authority on sundown towns, Sullivan was one of more than 200 communities in Missouri fitting that description. It was a way of keeping the townsfolk exclusively white, and its influence endured long after the end of legal segregation. The 2010 census records that Sullivan still has only 16 black residents 0.2% of its 7,000 population.

But it was the personal attacks that cut Wehmeyer deepest. When he joined the local high school, aged 13, he was puzzled as to why his classmates were talking about going coon hunting tonight. In his second year, a boy in his class called him a stupid nigger. When Wehmeyer complained, the teacher assured him that the N-word was a term of endearment. He stormed out of the classroom, and was suspended from school for two days for insubordination.

In his first away game with the school football team, he was sitting on the sidelines besides a fellow team member when the boy turned to him and said: You need to move seats if my dad finds me sitting with a nigger hell beat us both up.

Then one time he was out sledding in the snow and narrowly missed hitting a car owned by the parents of one of his classmates. The next day the father and son turned up at his door brandishing a handgun threatening to kill him.

That was, and still is, the world outside the Green Book. A world where children with dark skins are welcomed to high school with the endearing N-word and told they are going to die by adults wavingguns.

If thats what it was like in places not listed in the Green Book, then its no wonder that Alberta Elliss amenableestablishments were such a hit. She had a whole empire of black-friendly premises in Springfield, Missouri the town where Jonathan Herbert and Marlin Barber began that Facebook conversation lastsummer.

Official data compiled by the state shows that racial disparity in the frequency of vehicle stops by Missouri police has grown steadily since 2000. Today, AfricanAmericans are75% more likely to be stopped and searched than whites. Exercise extreme caution when travelling throughout the state was the travel advisory issued last summer by the Missouri branch of the civil rights organisation the National Association for the Advancement of Colored People.

For younger African Americans, racial profiling by police has become the new frontline in their experience of driving while black. Marshall Egson, whose family owns a large colonial-style house in Cape Girardeau, Missouri, which was listed in the Green Book, likens the cumulative effect of being stopped over and over again by law enforcement to post-traumatic stress disorder(PTSD).

Every time I go out in my car I worry: am I going to make it home? he says. Over time it gives you PTSD. The way I see it, most every black man in America has PTSD.

As the road miles of my tour of Missouri pile up, past and present seem to elide. When did the Green Book end and the present begin? Has there ever been a break?

In Springfield, the sense of history bearing down is palpable only a few blocks away from the former site of Albertas Hotel. It was here on Easter Sunday in 1906 that three young black men, wrongfully accused of raping a white woman, were lynched from a metal tower in the town square. The men were left hanging under a model of the Statue of Liberty perched on top of the tower.

Before the lynching, Springfield had a thriving black community that accounted for more than a third of the 60,000 population. Over the next couple of decades, most of the African Americans fled and Springfield became overwhelmingly white, as it remains to this day.

You could view the Easter Offering, as the lynching subsequently became known, as a buried historical detailwhose relevance is minimal. Or you could see a ghostly shadow of that tower still looming over the town, and directly reflected in the 2010 census records which put Springfields black population at ameagre4%, against the whites89%.

Jonathan Herbert had a powerful intimation of the legacy of the Easter Offering when he first moved to Springfield in 2005 to head the theatre programme at Ozarks Technical community college. He was struck by how small the black community was, and how unassuming its presence. It was like people were keeping their heads down. I felt that when I first got here, and I still do.

After Herbert and Barber put out their query on Facebook, igniting that passionate discussion among friends, Barber set out with his family on the road trip to Arkansas. They took to heart several recommendations gleaned from the conversation, including that they should bypass Harrison, an Arkansas town with a long history of KKK activity.

Having made those accommodations, everything went splendidly. When we finally took the trip we had no problems whatsoever, Barber says. I think that was partly because we had done our due diligence.

The modern equivalentof the Green Book had worked.

Barbers wife, Jaime, remains on edge. Over coffee in Springfield town square, she explains that whenever Marlin is late home from work she finds it hard to control the dread that wells up inside her.

Why is she so fearful?

I grew up in a small white town where certain words were used, she replies. I know the assumptions, the way they see black people.

Back in the former sundown town of Sullivan, Stefan Wehmeyer is now 22 and in a happier place. A couple of years ago he found religion, and has become a pastor in a local non-denominational church.

He says he is sticking with Sullivan, despite everything he was put through as a teenager. He sees it as his duty to remain in the town, in the trenches as he puts it, to combat local racial prejudice.

Thirteen weeks ago his wife, a white woman from a small town in Arkansas whom he met on a church mission, had their first child. Before their daughter was born, Wehmeyer prayed long and hard and was overawed in the delivery room when his prayer came true.

I prayed that shed look white, and she does, he says. She will besafe.